Key switch for electronic keyed instruments



N 1969 HISAYOSHI YAMADA ,7

KEY SWITCH FOR ELECTRONIC KEYED TNSTRUMENIS 3 Sheets-Sheet I Filed Oct. 30, 1967 f r v Port d sdziio o no #85054 N V- 25, 1969 HISAYOSHI YAMADA 3,480,744

KEY SWITCH FOR ELECTRONIC KEYED INSTRUMENTS 3 Sheets-Sheet :2

Filed Oct. 30, 1967 Nov. 25. 1969 HISAYOSHI YAMADA 3,480,744

KEY SWITCH FOR ELECTRONIC KEYED INSTRUMENTS Filed Oct. 30, 1967 3 Sheets-Sheet F i1 l0 'Pbo ' US. Cl. 200-1 United States Patent 3,480,744 KEY SWITCH FOR ELECTRONIC KEYED INSTRUMENTS Hisayoshi Yamada, Yokohama, Japan, assignor to Victor Company of Japan, Limited, Yokohama, Japan Filed Oct. 30, 1967, Ser. No. 678,816 Claims priority, application Japan, Oct. 31, 1966, 41/ 71,368 Int. Cl. H0111 9/00, 3/00; Gh 1/02 Claims ABSTRACT OF THE DISCLOSURE A key switch for electronic keyed instruments having keyboards for causing displacement of an operating rod connected to movable elements to effect switching with a restraining spring connected to the operating rod to restrain the operating rod from its displacement caused by the keyboard and with a control spring included between the keyboard and the operating rod and displaced beforehand by a given amount with the aid of means for adjusting displacement, said control spring being displaced when the load acting thereon from the keyboard exceeds a given value.

The present invention relates to a key switch, particularly a key switch interlocked with a keyboard of an electronic keyed instrument.

In general, electronic keyed instruments such as an electronic organ are required to produce sound and also minimize the increase of load caused by the downward movement of a keyboard when the free end of the keyboard is moved downwards to a position which is the total downward movement thereof. That is, the small increase of the load acting on the finger in case of moving downwards the keyboard by the finger ensures good finger touch and further provides the important advantage that good performance feeling can be obtained.

A conventional key switch for electronic keyed instruments makes use of means for directly interlocking the downward movement of the keyboard with the switch to close simultaneously a number of circuits, so that the load acting on the finger when the keyboard passes through a distance which is /3 the total downward movement thereof is comparatively small, but becomes suddenly increased when the keyboard further moves downwards through a distance which is equal to the total downward movement. Thus, the finger touch and hence the performance feeling becomes bad.

In order to obviate the above disadvantage the invention provides means included in the keyboard and the key switch and transmitting the movement of the keyboard to the key switch and also controlling the force acting on the finger in case of moving downwards the keyboard.

The principal object of the invention, therefore, is to provide an improved key switch for electronic keyed instruments, and which is adapted to be constructed so as to effect switching a number of circuits simultaneously with the aid of weak operating force.

Another object of the invention is to provide such an improved key switch for electronic keyed instruments which has a good finger touch in case of moving down- 3,480,744 Patented Nov. 25, 1969 'ice wards the keyboard and which can remarkably improve a performance feeling.

Yet another object of the invention is to provide such an improved key switch for electronic keyed instruments which can remarkably improve the shape utility of the switch and which is less expensive, small in size, and light in weight.

Other objects and features of the invention will appear in the following specification, reference being had to the drawings, in which:

FIG. 1 is a longitudinal sectional view illustrating a conventional key switch for electronic organs;

FIGS. 20, 2b and 2c are graphs explaining the operation of the key switch shown in FIG. 1;

FIG. 3 is a longitudinal sectional view illustrating a key switch for electronic organs embodying the invention;

FIG. 4 is a perspective view showing an essential part of the key switch shown in FIG. 3;

FIG. 5 is a plan view showing a part of the switch shown in FIG. 3;

FIG. 6 is its side elevation;

FIG. 7 is a front view showing a movable element of the switch; and

FIGS. 8, 9 and 10 show graphs for explaining the operation of the switch embodying the invention.

At first, a conventional key switch for electronic organs will be explained with reference to FIGS. 1 and 2.

With reference to FIG. 1, the conventional key switch comprises a base frame 11, a keyboard 12 secured at its base portion through a leaf spring 13 to the base frame 11, a switch 14 secured through a mounting plate 15 to the base frame 11, a plurality of movable elements 16 of the switch 14, stationary contacts 17 associated with the movable elements 16, and an operating rod 18 connected to each movable element 16 and adapted to be displaced by the keyboard 12 to bring each movable element 16 into contact with each stationary contact 17.

In such conventional electronic organ if the free end of the keyboard 12 is moved downwards each movable element 16 is brought into contact with each stationary contact 17 when the free end of the keyboard 12 arrives at a distance which is /a the total displacement thereof. This operating condition of each movable element 16 is shown in FIG. 2a. As shown in FIG. 2a the free end of each movable element 16 is bent downwards, so that the spring force of each movable element 16 acting on the operating rod 18 is comparatively small. Then, the keyboard 12 is caused to move downwards through the rest of the total displacement thereof, that is the total displacement thereof. This operating condition of each movable element 16 is shown in FIG. 2b. As shown in FIG. 2b that part of each movable element 16 which is connected to the operating rod 18 is deflected downwards, so that the spring force of each movable element 16 acting on the operating rod 18 becomes rapidly increased. Thus, the load acting on the finger for moving downwards the free end of the keyboard 12 becomes rapidly increased as shown in FIG. 20 and thus results in a bad finger touch.

The invention aims at to obviate the above mentioned disadvantage. Referring now to FIGS. 3-7 there are shown a switch 26 having a keyboard 23 secured at its base portion through a leaf spring 22 to a base frame 21 and causing displacement of an operating rod 30. Each movable element 27 is secured through mounting plates 24, 25 to the frame 21. The operating rod 30 is secured to each movable element 27 and slidably mounted in the mounting plates 24, 25. Between one end of the operating rod 30 and the frame 21 is connected a restraining spring 31 which serves to restrain the operating rod 30 from its displacement caused by the keyboard 23. A control spring 32 is included between the free end of a bracket 38 secured to the base portion of the keyboard 23 and another end of the operating rod 30. The control spring 32 is preferably made of a leaf spring having an inverted V-shaped cross section and secured at its one end to the operating rod 30 and engages at its another end with the lower end of the bracket 38. The force of the control spring 32 is made stronger than the force of the restraining spring 31, but weaker than the spring force of each movable element 27. The control spring 32 is displaced beforehand by a given amount with the aid of means for adjusting displacement 33 such that the control spring 32 will displace when the load acting thereon from the keyboard 23 exceeds a given value, thereby controlling the force acting on the finger.

The means for adjusting displacement 33 preferably comprises an adjustable spring 34 and an adjustable screw 35 as shown in FIGS. 3 and 4. The spring 34 is preferably made of a leaf spring having a V-shaped cross section as shown in FIG. 4. One end of the spring 34 is secured to the operating rod 30 and the other end is urged against the inner surface of the free end of the control spring 32. The adjustable screw 35 is adapted to displace the adjustable spring 34 so as to displace beforehand the control spring 32 by a given amount.

36 designates a lower mounting plate for mounting the base portion of each movable element 27; and 37 shows an upper mounting plate for mounting each pair of stationary contacts 28, 29 thereon.

The operation of the above mentioned key switch embodying the invention and having 8 circuits per one key as shown in FIG. 3 will now be described.

If the end of the keyboard 23 is moved downwards, the lower end of the bracket 38 secured to the keyboard 23 is caused to displace towards left direction and this displacement causes the operating rod 30 to displace through the control spring 32 towards the same left direction against the action of the restraining spring 31.

In this case the control spring 32 is so adjusted that it could not be displaced until the operating rod 30 and hence the restraining spring 31 are displaced a given distance.

The displacement of the operating rod 30 causes each movable element 27 connected thereto to displace from the contact 28 at one side to the contact 29 at the other side and urge against the latter.

After the operating rod 30, each movable element 27 and restraining spring 31 have been displaced through a given distance, they are no further displaced, but the control spring 32 is caused to be moved by the keyboard 23.

FIGS. 8-10 show changes of the load of the switch 26 acting on the finger in function with the total displacement of the free end of the bracket 38 secured to the keyboard 23, in which the total displacement H is plotted along the abscissa, while the load is plotted along the ordinate.

In FIG. 8 the curve I represents the load characteristic produced from each movable element 27 of the switch 26 and acting on the finger and its curve II represents the load characteristic produced from the restraining spring 31 and acting on the finger. FIG. 9 represents the total load characteristic produced from the switch 26 as a whole and acting on the finger. The load characteristic of the conventional key switch is represented by a curve OTSP-R resulted from the sum of the curves I and 11 shown in FIG. 8, while the total load characteristic of the key switch according to the invention is rep- .4 resented by a curve O-TS-P-Q. That is, in the key switch according to the invention the control spring 32 is separated from the adjustable spring 34 at that point P where the switch load exceeds the flexible force of the control spring 32 and thus results in the control spring 32 to-be started into its own deflection. Thus, the load characteristic acting on the finger is represented by the line PQ and hence the load of the switch 26 acting on the finger becomes considerably decreased from the load of the conventional switch represented by the dotted line P-R. Thus, it is possible to reduce the final load acting on the finger by an amount shown by Fo-F.

FIG. 10 shows load characteristics acting on the finger when the degree of opening of the control spring 32 is changed through the adjusting spring 34 by means of the adjusting screw 35. In FIG. 10 I represents the load characteristic when the degree of opening of the control spring 32, that is, the predetermined amount of displacement of the control spring 32 is large as shown by h, II represents the load characteristic when the degree of opening of the control spring 32 is intermediate as shown by h, and III represents the load characteristic when the degree of opening of the control spring 32 is small as shown by h". The more the degree of opening of the control spring 32 is the more the final load acting on the finger becomes.

In FIG. 3 if that part 39 of the frame 21 which is connected to the leaf spring 22 is bent upwards or downwards by a suitable degree, the load acting on the finger when the end of the keyboard 23 is moved downwards may accurately be adjusted by changing the degree of opening of the control spring 32.

Thus, the switch according to the invention makes it possible to switch a number of circuits by applying a force which is smaller than that applied to the conventional switch and considerably improve the finger touch necessary for switching by means of the keyboard. Moreover, the invention provides an economical way of incorporating an electric circuit element such as a resistor, a condenser etc. into the switch body as shown in FIGS. 3 and 6. For example, a resistor 40 may be mounted on the lower mounting plate 36 and one of the leads of the resistor 40 may be connected to the movable element 27. While another lead may be used as a switch terminal. Thus, the invention can be applied effectively to the fabrication of less expensive key switches which are small in size, and light in weight.

It will be appreciated that the invention is not restricted to the embodiments described and that many variations are possible to a person skilled in the art without departing from the scope of the invention.

What I claim is:

1. A key switch for electronic keyed instruments comprising a base frame, a keyboard secured at its base portion through a first resilient member to said base frame, an electric switch secured through a mounting member to said base frame and having a plurality of movable elements made of a resilient material and stationary contacts, an operating member adapted to be displaced by means of said keyboard and connected to each of said movable elements whereby each movable element is moved and brought into contact with each stationary contact, a second resilient member connected between one end of said operating member and said base frame for restraining said operating member from its displacement caused by said keyboard, and a third resilient mem ber positioned between the end of a bracket secured to the base portion of said keyboard and the other end of said operating member, said third resilient member being connected to said other end of the operating member, the spring force of said third resilient member being stronger than that of said second resilient member and weaker than that of the resilient member of said movable element.

2. A key switch as claimed in claim 1 wherein said third resilient member includes means for adjusting its spring force. 4

3. A key switch as claimed in claim 2 wherein said means for adjusting the spring force of the third resilient member comprises a fourth resilient member, one end of which is secured to the other end of said operating member and the other end of which is urged against the end of said third resilient member nearest said bracket, a screw adapted to displace said fourth resilient member, and means for adjusting the displacement of said fourth resilient member.

References Cited Fauser 84433 XR Gibbs et al.

Riggs et al. 84-l.27 XR Campbell et a1.

Lund 841.27 XR Schwartz et al.

Schwartz et al. 84433 10 ROBERT K. SCHAEFER, Primary Examiner J. R. SCOTT, Assistant Examiner UNITED STATES PATENTS US. Cl. X.R.

2,567,870 9/1951 Bozak et a1 29-630 XR 15 841.27, 433; 200--166 2,832,251 4/1958 Hayslett 84-433 

